XHC WHB04B development?

Okay. I did not really think that libusb_fill_interrupt_transfer() would solve the issue. But that IS the correct function to use in any case.

If the disconnect happens only at mode switches, I'm pretty sure it can be solved simply by modifying the xhc-whb04b-6 component. Maybe we need to add some more (temporary) logging to the component to pinpoint the issue.

It appears our dongle firmware is different by one version increment. But of course the hardware side is the important one for compatibility. I would think that there is a good chance that the hardware is compatible or the same.

I have added a bit more logging to the component..
The component is attempting to connect, it says, but I wonder if it actually tries and why that doesn't work.

Do you mean that the pendant did not recover in the above situation after you had commented out the assert line?

You could enable all logging by adding the "-a" option when loading the xhc-whb04b-6 component. It will write a lot of things to the terminal... which makes it easier to figure out if it gets stuck in some specific part of the code.

@Hakan:
Strange. Mine doesn't show anything. But it's an LHB04B-6 TX V3 (Wired version)
As much as I read, it should work the same, but might be not.

Starting with -Ha and commenting out github.com/LinuxCNC/linuxcnc/blob/master...whb04b-6/usb.cc#L209 it shows:

out 0x06fefdfe801800bc 060e0800161e0200 06008069006e0000
out size 24B hdr 0xfdfe dom 0xfe status 0x80 coord1 +0024.3772 coord2 +0008.7702 coord3 -0002.0000 feed 0105 spindle feed rate 00110

So it seams the values are sent. Might be my device has a different firmware. With Mach3, I tried already and I didn't see any value. I will try again with Mach4.

Short update on that, Hannes. 
While in auto mode and running a program it doesn't show F: nor S:
It does react on Feed+/- and Speed+/- but only on displayed values in the HMI, not the pendant display.
In Man mode it shows F: and S: in the way one expect.

Hmm, mine shows always 0. In Mach3, Mach4 and LinuxCNC.

I'm pretty sure I just have a variant with a different buggy firmware than yours.

However, if you have time to spare, you can comment out the line in my last post, recompile linuxcnc and send me the result. Which version of LinuxCNC are you using?